The present invention relates to a fermentation process for the preparation of cellulase. By this process, a good yield of cellulase at relatively low cost may be obtained, using cellulose-containing waste materials resulting from agricultural and forest industries as the carbon source.
The term "cellulase" used in this specification denotes both .beta.-glucanase (including endo- and exo-.beta.-glucanase) and .beta.-glucosidase. These are all well known enzymes which participate in the hydrolysis of cellulose.
It is known to obtain sugar-containing liquor by the cellulase-hydrolysis of cellulose, said cellulase being obtained by fermentation of a microorganism of the genus Trichoderma. Various strains of Trichoderma reesei have been found to be particularly suitable for this purpose in view of the titre of cellulase obtained and the ratios of the three above-mentioned enzymes present in the accumulated cellulase, for example, Trichoderma reesei QM9414 (ATCC 26921). However, known processes of this type which use Trichoderma reesei strains are not always satisfactory, since the amount of accumulated cellulase may vary depending upon the cellulose-containing material used as the carbon source. If, for example, bagasses or rice straws, from which lignin has been removed, are used as the carbon source, a lower level of cellulase production is sometimes noted as compared to when the carbon source is Avicel or a cellulose powder containing a large amount of crystalline cellulose.
Whilst Avicel and cellulose powders are often used as carbon sources for the industrial preparation of cellulase by fermentation because they are good carbon sources, they have the disadvantage of being extremely expensive compared with other cellulose-containing raw materials. There is therefore a need to provide a more economical process for the preparation of cellulase using if possible cheaper waste materials, e.g. from agricultural and forest industries as the carbon source.